Short arc lamp with ignition means and envelope sealing means



- 1 1970 n. R. SIMON ET L SHORT ARC LAMP WITH IGNITION MEANS AND ENVELOPE SEALING MEANS Filed Feb. 9. 1967 INVENTOR Ange/0 J. Guern'er/ Dona/0 R Simon ATTORNEY United States Patent Oflice 3,534,213 Patented Oct. 13, 1970 U.S. Cl. 313-184 4 Claims ABSTRACT OF THE DISCLOSURE Method and apparatus for producing one shot, high pressure, electric arc illumination of subminute lifespan comprising a quartz tube which encases a pair of confronting electrodes in a noble gas atmosphere, and which is sealed by a pair of relatively heavy end caps. The end caps serve to maintain the electrodes in rigid axial alignment, and act as heat sinks when the lamp is in operation. They are sealed to the tube by epoxy resin, the seals degrading and terminating operation of the lamp at a predetermined design time. A fine, spring wire coupler is interposed between the electrodes to ignite the are when "current is applied thereto.

It is the object of this invention to provide a small,

reliable, low-cost, one-shot, arc lamp of limited lifespan,

which is capable of withstanding severe vibration and acceleration forces.

It is a further object to attain a lamp of predetermined, continuous operation lifespan, by equipping it with heat sinks and utilizing heat degradable sealing material, which latter terminates operation of the arc upon breakdown.

A further essential object of this invention is to provide a novel igniter coupler b tween the electrodes which is expended in igniting the arc, when current is applied thereto.

Short arc lamps are known in the prior art in a variety of structural forms such as shown in U.S. Pats. to Beese, No. 3,005,923, of Oct. 24, 1961; Lye, No. 3,054,921 of Sept. 18, 1962; and Fredrich, No. 3,259,778 of July 5, 1966. However, none of the above are designed to meet the requirements as to shock, measured lifespan, and ignition characteristics of the subject invention; nor are they expendable, one-shot devices. Arc lamps approaching the later requirements are disclosed in prior US. Pat. to Keller et al. No. 3,274,427, but these too lack the structural characteristics and functional properties which distinguish the present invention, particularly as to rigidity and controlled lifespan. The are lamp of the subject invention is so structured as to withstand forces of 1000 g., to have a measured lifespan of approximately 35 seconds, and to give off visible radiation on the order of 120 watts.

With the foregoing requirements and with the objects of the invention stated above in mind, the invention will be described in connection with the figures of the drawings in which FIG. 1 is an elevation of the subject invention, with parts cut away in section.

FIG. 2 is a detail section of an end cap of the lamp, on an enlarged scale.

FIGS. 3 and 4 are enlarged views of the igniter spring.

Referring to FIG. 1, the subject arc lamp comprises a quartz tube 5, stainless steel caps 6 and 6a, thoriated tungsten electrodes 7 and 8, and terminal conductors 9. The stainless steel caps are machined to three different interior diameters 10, 11 and 12, the smallest of which, 10, receives an electrode, the intermediate one, 11, accepts the end of the quartz tube, and the largest one, 12, provides a concentric space surrounding the quartz tube for reception of epoxy resin seal 13. The caps are of sufliciently heavy construction to serve as heat sinks and are poor enough heat conductors to retard heat transmission to the epoxy seals; the electrodes are brazed to the caps and the terminal conductors 9 are silver soldered to the caps and electrodes as shown at 13a;

One of the caps, the right hand one in FIG. 1, shown on an enlarged scale in FIG. 2, is bored off-center as shown at 14, the larger diameter of bore 14 receiving a short bronze nipple 15 which is silver soldered therein, and which serves for evacuation of air from the envelope and for filling the same with a noble gas such as xenon. This nipple is pinched off and heat sealed as shown at 16, FIG. 1, upon introduction of noble gas, under suitable pressure (on the order of 3-10 atmospheres), into the lamp assembly.

A single convolution coil of tungsten spring wire 17 spans the arcing space intermediate electrodes 7 forming a compression spring therebetween. The terminal portions of the coil comprise integral loops 17a which encircle the tips of the electrodes and provide good electrical contacts therewith, as shown. The are separation between the electrodes is on the order of .005" and the starting spring wire is .005" in diameter.

In assembling the lamp, electrodes 7 and 8 are brazed to caps 6 and 6a, respectively, the terminal conductors are silver soldered as is the nipple 15 in cap 6a. The two electrodes are then inserted into the quartz tube with spring 17 between them and the caps are sealed thereto by epoxy resin seals 13. Upon evacuation and filling with noble gas, nipple 15 is sealed off.

In operation, power is applied from a DC. source 18 upon closure of switch 19. Coil spring 17 heats and melts; in so doing it ignites an electric arc between the electrodes, which continues in operation until sufficient degradation of the epoxy resin seal takes place and the pressurized gas atmosphere within the envelope is lost. As previously indicated the subject lamp is of miniature dimension, the exterior diameter of quartz tube 5 being on the order of .325" and the overall length of the assembly of 2". The heat generated by the arc during operation is conveyed by the electrodes, the quartz tube and gas convection to the heat-sink caps 6 and 6a, and ultimately to the epoxy seals. The latter deteriorate and break down in less than one minute of. operation.

Since the wire diameter of starting coil 17 is very small, its fusion and melting upon ignition of the arc causes no significant fogging of the quartz tube and does not materially impair the light value of the arc.

A further significant characteristic of the starting coil resides in its dynamic fastening to the electrodes which is capable of withstanding shock and vibration, and which eliminates the need for welded connections of its terminals to the electrodes.

While a preferred embodiment of the invention has been disclosed in the foregoing, it will be understood that modifications within the spirit and scope thereof may be made falling within the range of the claims which follow.

What is claimed is:

1. A one shot, electric, short arc lamp comprising a transparent envelope, a pair of heavy heat-sink caps at the ends thereof, electrodes rigidly embedded in said caps, pressurized noble gas filling within said envelope, a springlike mechanical arc ignition means bridging the discharge ends of said electrodes and frictionally supported solely thereby, power supply terminals affixed to said electrodes, and fluent self-setting seal means retaining said caps on said envelope.

2. A device according to claim 1 in which the heat-sink caps are of stainless steel, and in which the seal means retaining said caps on the envelope is an epoxy resin.

3. A device according to claim 1 in which the fluent, References Cited selfk-lsczttigg seal trlneans cczimprises a1 sealant tcapalglef of UNITED STATES PATENTS wit s an mg a c osen pre e ermine empera ure e ore breakdown and in which the heat generated by the arc 2259053 10/1941 Xems 337 159 is conveyed by the electrodes, the envelope and convecr FOREIGN PATENTS tion of the noble gas to the heat-sink caps and thence to o the sealant causing degradation of the latter, with con- 945,482 1/ 1964 GEM Bntalnse uent f th bl s from the n 10 and fg g g g g 6 ve p6 JAMES W. LAWRENCE, Primary Examiner 4. In a device according to claim 1 wherein the electrodes have tapering discharge tips and the spring-like mean comprises a coil spring having seating loops at each 1 US. Cl. X.R. end thereof which compressionally engage said tapering 220 314 34 tips.

10 P. C. DEMEO, Assistant Examiner 

